Identifying and mapping an active topology of a computer network, e.g., a bridged Ethernet network, is a key requirement for service OAM (Operations, Administration, and Management). In particular, certain networks, such as carrier Ethernet (bridged) networks, tend to be complex, large in geographic reach, and often span multiple organizations, and as such, mapping the active topology (e.g., of a given virtual local area network, “VLAN”) is a challenging task. Many network management systems (NMS) today rely on polling individual devices (network elements) for the purpose of mapping the active topology of a given service or VLAN. This is an out-of-band operation that is slow, tedious and error-prone. Ideally, it is desirable to be able to build the topology map on a given network element by relying on in-band protocol mechanisms.
As an alternative, the IEEE standard 802.1ag-2007 defines a “Linktrace” protocol, which allows the dynamic discovery of a path between a Maintenance End Point (MEP) and another MEP or a Maintenance Intermediate Point (MIP) on a given VLAN using in-band protocol mechanisms. A network administrator can issue a series of one-by-one Linktrace messages to determine the routes to each MEP that has been discovered, and thus map the network. However, this process suffers from the same set of shortcomings as the NMS polling mechanism mentioned above. In addition, should there be any misconfigurations (e.g., improper MEPs) or if an MEP has failed to “come up” (that is, it was not initially discovered due to being failed/down), then the Linktrace messages will not be propagated properly, and the Linktrace operation is ineffective.